Radio frequency (RF) switches, such as field effect transistor (FET) type RF switches disclosed in U.S. Pat. No. 9,755,063, are devices commonly utilized in wireless communication devices (e.g., smart phones) to route signals through transmission paths between the device's processing circuitry and the device's antenna. Phase-change materials (PCM) are capable of transforming from a crystalline phase to an amorphous phase. These two solid phases exhibit differences in electrical properties, and RF switches can advantageously exploit these differences. However, the capability of phase-change materials for phase transformation depends heavily on how they are exposed to thermal energy and how they are allowed to release thermal energy. For example, in order to transform into an amorphous phase, phase-change materials may need to achieve temperatures of approximately seven hundred degrees Celsius (700° C.) or more, and may need to cool down within hundreds of nanoseconds.
Heating elements in PCM RF switches often contribute to parasitic capacitances associated with RF frequencies and result in performance tradeoffs. RF terminal interconnects, such as interconnects disclosed in U.S. Patent Application Publication No. 2018/0068941 A1, in RF switches also contribute parasitic capacitances.
Fabricating RF terminals for PCM RF switches without significant RF performance tradeoffs becomes complex, especially where the PCM RF switches are designed primarily around thermal performance. Accordingly, accommodating PCM in RF switches can present significant manufacturing challenges. Specialty manufacturing is often impractical, and large scale manufacturing generally trades practicality for the ability to control device characteristics and critical dimensions.
Thus, there is a need in the art to simply and reliably manufacture PCM RF switches having low parasitics.